1. Field of the Invention
The present invention relates to vehicle an air conditioning apparatus which is capable of independently controlling the temperature of air from each of a face air outlet and a foot air outlet.
2. Related Art
Conventionally, a vehicle air conditioner, such as automatic air conditioners, computes the required air supply temperature based on the inside and outside temperatures of a passenger compartment and the temperature set by a temperature setting device, and controls a supply airflow ratio of the face air outlet and the foot air outlet in accordance with the computed result. As a result of this control being performed, a foot mode wherein heated air is concentrately supplied from the foot air outlet to a compartment floor of the vehicle is set and operated when the outside temperature is low, such as in winter.
In a conventional vehicle air conditioner, a correction control is performed where the required supply air temperature (i.e., the temperature of conditioned air) is lowered because of an increased amount of sunlight.
In such an air conditioner, in case a comparatively strong amount of sunlight shines on the upper half of a passenger while the foot mode is selected, namely, in a case where it is preferable to soften a warm or hot feeling of the upper half of the passenger's body with conditioned air, the temperature of the conditioned air is lowered by the above correction control. However, the conditioned air from the foot air outlet hardly reaches the upper half of the passenger's body. So, there are problems in that it is impossible to soften the excessively warm or hot feeling caused by the insolation to the upper half of the body and an air conditioning feeling is deteriorated. Further, since the correction control lowers the temperature of the conditioned air, a lack of heating to the lower half of the passenger's body may be caused by the lowering of the temperature of warm air from the foot air outlet.
A solution to these problems can be seen from the air conditioner shown in Japanese Patent Application Laid-Open Publication No. Sho 57-15009, and its U.S. Pat. No. 4,417,618 therein, in the foot mode, when the amount of sunlight is equal to or more than a predetermined level, a bi-level mode is automatically set and operated. In that mode conditioned air is supplied from both the face air outlet and the foot air outlet, and thereby the warm or hot feeling of the upper half of the body of the passenger is alleviated and the air conditioning feeling is improved.
In most air-conditioners, an airflow ratio of the face air outlet and the foot air outlet in bi-level mode is generally set to 1:1. In the above described air conditioner, when the bi-level mode is set and operated after the amount of sunlight in the compartment becomes equal to or more than the predetermined level, a supply airflow quantity from the face air outlet increases quickly from zero. In such a case, however, an effective temperature to the upper half of the body of the passenger is lowered in accordance with the increase of the supply airflow, and it gives the passenger an unnecessary cool feeling because the temperature of the conditioned supply air is maintained the same. That is to say, it is hard to keep a linear relationship between a correction quantity conditioned air temperature based on the amount of insolated sunlight and a conditioned temperature which a passenger feels, and the air conditioning effect may be thereby deteriorated. Especially, it becomes particularly apparent, when a correction control lowers the temperature of conditioned air in accordance with the increased amount of sunlight into the compartment. In case that there is no mechanism for switching the foot mode to the bi-level mode when the amount of sunlight is equal to or more than the predetermined level and the correction control of the temperature of the conditioned air, it is also hard to keep the linear relationship between a correction quantity of conditioned air temperature by the amount of sunlight and the conditioned temperature which the passenger feels when supply airflow quantity from the face air outlet is controlled in accordance with the conditioned air temperature, and the air conditioning feeling may be deteriorated.
Even in case that the conditioned air temperature is adjusted by a temperature setting device in the hi-level mode in the conventional air conditioner, the air conditioning effect may be also deteriorated, because it is hard to keep a linear relationship between a variation quantity of the conditioned air in accordance with the set value and the conditioned temperature which the passenger feels.